Problem: Which of these numbers is composite? ${2,\ 3,\ 59,\ 61,\ 87}$
Answer: A composite number is a number that has more than two factors (including 1 and itself). 2, 3, 59, and 61 each have only two factors. The factors of 87 are 1, 3, 29, and 87. Thus, 87 is the composite number.